The recent characterization of proteins associated with synaptic transmission provides the opportunity to explore, in detail, the transport and localization of synaptic components during synaptogenesis. One of the challenges of such analysis is the ability to relate observations in vitro, where simple model systems may yield detailed information, with those normally occurring in vivo. We will explore questions of protein expression and redistribution in a model system, the rodent sympathetic ganglion, both in vivo and in vitro. Redistribution of protein in developing neurites, growth cones and terminals will be studied in vitro using high resolution confocal microscopy and image analysis, using immunocytochemical approaches. These studies will be compared with studies of normal synaptic development of the same population of neurons in vivo. These studies will make use of Yellow Fluorescent protein (YFP) coupled fusion proteins to provide an additional measure of terminal development. What are the relationships between synthesis and transport of synaptic proteins, and the development of functional transmission? Are vesicle-associated and presynaptic membrane proteins assembled at terminal regions with similar time courses? Is synaptic protein content influenced by cellular phenotype? What is the role of membrane depolarization in regulating expression and redistribution of these proteins? Determining whether transsynaptic factors are important for regulating not only expression of these proteins but also their redistribution to developing synapses may have profound implications understanding developmental disorders of the nervous system, since assembly of components into complexes appears to be necessary for function. Neurons from rodent sympathetic ganglia are an attractive model in which to conduct studies of synaptogenesis, because of their accessibility, their ease of culture, and the wealth of background information concerning morphological and physiological development.